Easy call-
Even though fielder may have showed above average effort fielding the ball, if he comes up clearly in time to otherwise make an out on the batter runner at first then it is scored a fielders choice. The only way this play is recorded as a "hit" is if the first baseman cant make a play at first on the batter runner with ordinary effort. Ordinary effort starts the moment each segment of the play occurs. For instance, if the first baseman shows above average effort and it glances off his glove and a play cant be made at first, then walk off base hit. If he dives, makes above average effort, comes up cleanly in time to throw to first to retire batter runner, "ordinary effort" applies starting there at that point regardless of what happened prior. Thus, because he could have retired batter runner with ordinary effort at that point but chose instead to fire home, it is recorded as a walk off fielders choice, credit batter with a rbi and fc and at bat.